This invention relates to large forging presses of the pull-down type and, particularly, to an arrangement of such forging press by which removal of the large hydraulic cylinders from the foundation pit of the press is facilitated.
The present invention is closely related to the subject matter described in patent application Ser. No. 821,790 entitled "A FORGING PRESS WITH ADJUSTABLE DAYLIGHT AND WITH YOKE DESIGN FOR ATTACHING TIE-RODS TO CROSSHEADS" which is commonly assigned with the present application. The subject matter thereof is incorporated herein by reference.
Forging presses are used for shaping a metallic workpiece into an end product of desired shape by pressing said workpiece between two facing die halves to give the workpiece an intended shape.
Various types of forging presses are known. The concept of the present invention is however most suitable for a pull-down forging press which includes a very large steel frame surrounding a stationary bridge, the frame being movable up and down relative to the bridge. The frame has a top which extends horizontally above the bridge, a bottom below the bridge and sides which connect the top and bottom of the frame to one another. The top and bottom members of the frame are known in this art as the upper and lower crossheads, respectively, while the sides are commonly referred to as the columns or tie-rods of the frame.
So-called return cylinders stand on the bridge and support the upper crosshead of the frame, providing a clearance between the upper crosshead and the top of the bridge. During a certain position of the operating cycle, pressure in the return cylinders is reduced, and the pistons or rams of the return cylinders are lowered, resulting in the workpiece being abutted between the bridge and the upper crosshead of the frame. The metallic workpiece is located on a first die half which is located on the bridge while a facing die half which is secured to the top of the frame projects from above. Although the entire weight of the frame, weighing as much as several hundred tons can be applied to the workpiece, the forging operation under certain circumstances, may require much larger forging forces. The required forces may reach, depending on the press rating, several hundred kilotons; moreover, the forces must always be applied under controlled conditions.
Therefore, the forging press pressures are generated by a plurality of main cylinders which are disposed beneath the bridge, on the lower crosshead of the frame. When the main cylinders are operated their pistons extend, and being braced against the bottom of the bridge, the frame is pushed downwardly with great force. Consequently, the metallic workpiece located above the bridge is forced to assume a shape of the die cavity.
Conventionally, the stationary bridge of the forging press is located at about ground level. The portions of the frame which extend below the bridge and the main cylinders are housed in a foundation pit. The main cylinders are quite large and heavy. In a forging press of the type to which the present invention is directed, there are typically as many as six, nine, or more such cylinders each weighing in excess of 100 tons, sometimes more than 350 tons. To save space, the cylinders are arranged in a tight configuration in the foundation pit.
A severe shortcoming of the above described forging press arrangement consists in that whenever any one of the main cylinders requires repair or replacement, the task of removing such main cylinder from the foundation pit involves an operation which, experience has shown, consumes many days, resulting in a shutdown of the forging press for an unduly long period.